David,
If I were going to do something like that, I would consider several things.

The first thing is how would your rear swing,tilt mechanism, and focusing track work with a larger (wider back). Most cameras attach to the sides of the rear wood standard and this then requires the metal becoming involved in the process. It can be as simple as building extensions to what is already there or it may mean a whole refabrication of that part of the camera.

The next thing is that it would require at the very minimum a table saw, jointer, and jig or saber saw to do the wood portion of the conversion. It would require the ability to do the box joints at each of the corners. There is a good site on the net that covers a jig that can be built to do the box corners. If the tools are available the wood isn't that difficult.

The conversion would require a new bellows.

Does Wisner's back include all of the metal, bellows, and wood for the conversion or is it just the wood back? If it is just the wood back I would look to what all of the additional items would cost. If it is the complete conversion at 2K then it may not be a bad price considering all of the work involved in building the componants yourself.

I hope that I have answered your questions or at the minimum given you directions in which to look. I agree that an ULF is appealing.

Best Regards,
Don Miller